The Role of the Subcutaneous Fat Index in Predicting Transforaminal Epidural Steroid Injection Treatment Success: An Observational Prospective Study.

Background: Obesity is thought to be one factor that contributes to low back pain (LBP). Classifying obesity according to body mass index (BMI) and its use in general health-related predictions is often considered inadequate. For this reason, a new parameter known as the subcutaneous fat index (SFI) has been defined to provide insight into spine health. SFI is the thickness of subcutaneous fat tissue (SFTT) at the L1-L2 level.

Objectives: This study aimed to investigate the answer to the question "Is this new index, which has been shown to be successful in predicting spinal degeneration and morphological changes, effective in predicting the success of transforaminal epidural steroid injection (TFESI) treatment?"

Study design: An observational prospective clinical study.

Setting: A university hospital's interventional pain management center.

Methods: Patients with spinal radicular pain due to intervertebral disc herniation, for whom TFESI was planned, were categorized into two groups according to SFI (was measured as the vertical distance from the tip of the spinous process of the L1 vertebra to the skin on axial T2-weighted lumbar spine magnetic resonance images cut-off values (9.4 mm in men and 8.45 mm in women) and were followed up for 3 months after the procedure. During patient follow-up, evaluations were performed with the Numeric Rating Scale, Oswetry Disability Index, and 12-Item Short-Form Health Survey. Additionally, intervertebral disc degeneration (IVDD) related to injection level and nerve compression grading were evaluated radiologically.

Results: A total of 50 patients' IVDD as related to injection level was significantly higher in the SFI > 9.4/8.45 mm group. According to the 3rd month's follow-up results, significant treatment success was observed in all parameters in both groups. However, no significant difference was found in predicting treatment success between the SFI < 9.4/8.45 mm and SFI > 9.4/8.45 mm groups.

Limitations: Our sample sizes were asymmetric, and a single radiologist performed the evaluation.

Conclusion: The newly defined SFI parameter was not effective enough to provide a significant difference in nerve compression grading or in predicting treatment success.